1. Technical Field
The present invention relates to a circular body, a circular body unit, and an image forming apparatus.
2. Related Art
As an image forming device using an electrophotographic system, an image forming apparatus which forms an electrostatic latent image on an image support, such as an electrophotographic photoconductor, develops the electrostatic latent image with a toner, electrostatically transfers the obtained toner image to an intermediate transfer belt which is an endless belt (primary transfer process), and transfers the same again to a transfer-receiving medium such as transfer paper (secondary transfer process) to form an image, has been conventionally known. In particular, in an image forming device using a system (tandem system) for obtaining a fill color image by overlapping different colored toner images upon each other, an intermediate transfer belt has been preferably employed. In this kind of image forming apparatus, an electrically conductive intermediate transfer belt having electrical conductivity has been widely used.
In the intermediate transfer belt, electrical properties, such as surface resistivity and volume resistivity, are important in addition to mechanical strength, such as flexibility, bending resistance, and tensile breaking strength, in order to obtain an output image which is stable and favorable over a long period of time.
For example, an image forming apparatus has been proposed which uses a metal primary transfer roll and in which the surface resistivity (ρs) is controlled to 9≦ρs≦12 and the sum of the inner surface roughness of an intermediate transfer belt and the surface roughness of the primary transfer roll is adjusted to 1.2 μm or less.
Moreover, an example is disclosed in which, in a two-layer intermediate transfer belt, transferring properties are improved by adjusting the thickness of a belt upper layer to from 5 μm to 50 μm; adjusting the thickness of a lower layer (base layer) to from 50 μm to 200 μm; adjusting a ratio of the surface resistivity (ρs) of the upper layer to the surface resistivity (ρs) of the lower layer to 1000 or more; and adjusting the surface resistivity (ρs) of the upper layer to 13.0 Log Ω/□ or more.
Furthermore, an example is disclosed in which, in a two-layer intermediate transfer belt, toner scattering is suppressed by controlling the volume resistivity (ρv) of a belt upper layer to be higher than the volume resistivity (ρv) of a lower layer.